1. Field of the Invention
The present invention relates to a surface-mounted oscillator, and more particularly, to a technique for reducing the planar dimensions of the surface-mounted oscillator.
2. Description of the Related Art
Since a surface-mounted oscillator is small-sized and lightweight, it is, for example, included in a portable appliance, and widely used as a frequency or time reference source, etc. For example, if a portable appliance to be used is a telephone, a temperature compensated oscillator (TCXO) disclosed by Patent Document 1 is used because of its dynamic environments.
A surface-mounted oscillator is configured to accommodate, in a surface-mounted package, an oscillation element such as a crystal piece, etc., an IC (Integrated Circuit) chip in which an oscillation circuit, a temperature compensation circuit, etc., are integrated, and a circuit element composed as a discrete component such as a capacitor, etc., which cannot be integrated within the IC chip.
FIGS. 1 to 3 are cross-sectional views showing the internal configurations of normal surface-mounted oscillators.
FIG. 1 shows a surface-mounted oscillator recited in Patent Document 2. In this oscillator, an oscillation element 1, an IC chip 2, and a circuit element 3 composed as a discrete component such as a capacitor, etc. are integrally accommodated in a surface-mounted package 4 of a so-called H structure type.
The surface-mounted package 4 is configured by comprising concave portions on both of its main surfaces, and by integrating an oscillation element 1, which is sealed with a cover 9 after being accommodated in the concave portion on one of the main surfaces, and the IC chip 2 and the circuit element 3, which are accommodated in the other concave portion.
FIG. 2 shows a surface-mounted oscillator recited in Patent Document 3. The surface-mounted oscillator shown in this figure has a configuration of a junction type, where a surface-mounted package 4 is separated into a package 5 and a mounting board 6, and the concave mounting board 6 in which an IC chip 2 and a circuit element 3 are accommodated is joined to the bottom of a crystal oscillator configured by hermetically sealing an oscillation element 1 with a cover after accommodating the oscillation element 1 in the package 5.
FIG. 3 shows a surface-mounted oscillator recited in Patent Document 4. The surface-mounted oscillator shown in this figure has a configuration of a single space type, where an IC chip 2, a circuit element 3, and an oscillation element 1 are hermetically sealed with a cover 9 in the same space after the IC chip 2 and the circuit element 3, and one end of the oscillation element 1 are respectively secured to the bottom of a concave portion of a surface-mounted package 4, and to a stage portion on an inner wall of the concave portion in the surface-mounted package 4.
[Patent Document 1]
Japanese Patent Publication No. 2000-244243
[Patent Document 2]
Japanese Patent Publication No. HEI8-204452
[Patent Document 3]
Japanese Patent Publication No. 2003-179433
[Patent Document 4]
Japanese Patent Publication No. HEI9-298440
Currently, the planar dimensions of a surface-mounted oscillator are, for example, on the order of 3.2 by 2.5 mm, but there is a demand for further reducing the dimensions. Additionally, as an oscillation frequency increases, the size of an oscillation element 1 such as a crystal piece, etc. becomes smaller. However, there is a problem that an increase in planar dimensions cannot be avoided, because an IC chip, and a discrete component such as a capacitor, etc. are arranged on the same flat surface.